This invention relates to an analog space-time relay method and apparatus for a wireless communication channel.
Wireless relays have shown potential for extending communication range and providing good quality of experience. In general, there are two broad relay schemes which can be categorized based on the processing done at the relay stations: digital domain processing and analog domain processing. The “decode and forward” (DNF) scheme is a digital domain processing scheme that has been shown to remove noise at the relay station, although it demands intensive signal processing at the relay nodes. The DNF scheme has also been classified as a “regenerative” relaying scheme where the signal has to be “regenerated” for transmission. The signal received at the relay station from the source is decoded and where errors are present in the decoded signal, these errors will be propagated from the relay station to the destination.
In relation to analog signal processing schemes, the “amplify and forward” (ANF) is an analog scheme that is very simple, but has shown a disadvantage where noise collected at the relay is amplified and transmitted to the destination along with the desired signal.
Another way of performing relaying would be to use a distributed space-time coded (DSTC) scheme where higher diversity may be achieved than that of simple ANF and DNF. DSTC can be implemented using either ANF or DNF schemes. DSTC however suffers from the same disadvantages as that of ANF or DNF i.e. when implemented using ANF, noise collected at the relay is amplified and transmitted on to the destination, and when implemented using DNF, decoding errors at the relay station are propagated from the relay station to the destination.
It is an object of the present invention to provide an analog space-time relay method and apparatus which addresses at least one of the problems of the prior art and/or to provide the public with a useful choice.